By the Light of the Moon

Luna pairs with Jupiter and glows with Earth’s light

By J. Alex Knoll

A nascent crescent moon emerges from the lingering glow of sunset at week’s end and then appears roughly 10 degrees higher and remains visible a half-hour longer night by night. Saturday evening, the moon forms a near perfect triangle with blazing Jupiter to the east and orange Aldebaran to the south, each less than 10 degrees from the other.
Sunday the moon pulls within two degrees of Jupiter, and the pair remain visible until 10:30pm. Even just a few days old, the waxing moon, at magnitude –10.6, is exponentially brighter than Jupiter at magnitude –2.1. Below Jupiter, look for the stars of the Pleiades cluster, shaped like a miniature dipper.
As Jupiter dips toward the northwest horizon, Saturn climbs into view in the southeast. As the ringed planet nears opposition at the end of the month, its visage only improves. Binoculars will reveal the planet’s rings as a pronounced bulge, while even a modest telescope will bring them into enough detail to differentiate several of the larger rings.
Any telescope you use is likely stronger than that of Dutch astronomer Christiaan Huygens, who in 1655 first discerned the band encircling Saturn to be separate rings. Huygens also discovered Saturn’s largest moon Titan, the only satellite known to have an atmosphere, albeit one of methane. At magnitude 8, Titan is invisible to the unaided eye but is easily seen even with good binoculars. Watch Titan this week as it inches from west to east across the face of Saturn. Spring’s waxing crescent moon offers its own rare sight: earthshine, which appears as a faint glow on the un-illuminated face of the moon. While the moon’s normal glow is a result of sunlight reflecting from its surface, earthshine occurs when sunlight is reflected from the planet’s surface back to the moon.